The present invention relates to an apparatus for driving fastening elements and, in particular, to a fastener driving apparatus with a hammer piston.
In many known apparatuses of this type, the loading of the fastening elements is carried out through the mouth of the apparatus, which displays disadvantages which manufacturers intend presently to eliminate.
Whether it concerns nails or other fastening elements, for instance self-boring fasteners, the forward end of the fastener is in the shape of a point upon which the operator must push in order to introduce, or load, the elements into these apparatuses, this entailing the risk of injury. Of course, by using a specialized tool for this loading operation, the risk of injury is eliminated, but this creates a new disadvantage which is the necessity of having such a tool immediately available.
Further, in the case where the fastening element is loaded through the muzzle, or front part, of an apparatus with such a specialized tool, the foreward end of the fastening element is in contact with the material intended to receive it, prior to impact on the element by the hammer piston, so that the penetration of the fastener into the material begins at a very low speed, which is detrimental to the quality of the fastening.
Apparatus of the type wherein the fastening elements are loaded through an opening formed in the barrel are known in the art, as, for example, U.S. Pat. Nos. 2,930,042, 2,936,455 and 2,970,314. While the first disadvantage hereabove mentioned is eliminated, such tools suffer in that the opening, when closed for firing, is not filled up and a discontinuity in the guide for the fastening elements arises in this area.
It has been attempted, for example, in U.S. Pat. No. 3,357,617 to reduce the disadvantage of the prior apparatus by the provision of a sliding element which fills up the loading opening during firing. Such tools, however, tend to be very fragile.
Two further approaches have been taken toward solving the above-described problem.
One of them, described in U.S. Pat. No. 3,172,119, comprises fixed means for receiving and guiding a fastening element, propelling means for a driving piece, and a barrel containing the driving piece and pivotally mounted about an axis parallel to the gun in order to be either aligned with the whole assembly of said means, or being moved to a lateral loading position in which the rear part of the fixed receiving and guiding means are accessible for loading the fastening elements.
The other, described in French Pat. No. 2,336,216, comprises a pivoting feeding device used for introducing the fastening elements into the barrel.
With these last two types of apparatus, an operator does not run the risk of injury during loading of the fastening elements, and a fastening element can penetrate the receiving or target material at a sufficient speed. The necessity for the operator to manually pivot the barrel of the feeding device, however, makes the handling of such apparatus particularly delicate and complicated.
Finally, other patents, such as French Pat. Nos. 1,469,786, 1,531,056 and 1,581,949, disclose apparatuses having barrels provided with muzzles for guiding the fastening elements, said barrels being pivotally mounted about axes orthogonal to the gun axis so as to provide access to the rear of the guiding muzzle for introduction of fastening elements therein. Such apparatuses solve the general problem mentioned hereabove. However, the pivoting of their guiding muzzles requires manual intervention which is a handicap to their use.